System Archetypes are patterns of behavior of a system. Systems expressed by circles of causality have therefore similar structure. Identifying a system archetype and finding the leverage enables efficient changes in a system. 

More info here: http://wwwu.uni-klu.ac.at/gossimit/pap/sd/wb_sysarch.pdf

Ten archetypes are generally acknowledged as forming the set of tools that reveal patterns of
behavior in systems.

* LimitsToGrowth (aka LimitsToSuccess)
* ShiftingTheBurden
* ErodingGoals
* Escalation
* SuccessToTheSuccessful
* TragedyOfTheCommons
* FixesThatFail
* GrowthAndUnderinvestment
* AccidentalAdversaries
* AttractivenessPrinciple

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TheFifthDiscipline CategoryPattern